Re: Freezer Current Safety Indicator?
- From: "Joe G \(Home\)" <joe.g@xxxxxxxxxxxxxxx>
- Date: Sat, 21 Apr 2007 01:32:02 +1000
"Jones" <at@xxxxxxxxxxxxx> wrote in message
news:2007042009194716807-at@xxxxxxxxxxxxxxx
Hello, all,
I have a chest freezer that I keep in an outbuilding.
On at least one occasion, for whatever reason (lightning?), this freezer
has thrown a breaker, cr@pped out (without us knowing it) and stunk up the
garage with rotten food and bait.
Some times old fridges have motors, whost startup current peaks a causes the
breaker to kick in.
**** Disclaimer ****
*****If you are not experienced in electronics AND electrical safety then
do not attempt these suggestions *****
**** Tinkering 240V ac / 110Vac mains voltage can be hazardous to your
health! ****
**** If any of this is unfamiliar then seek electrical professional help
before attempting any thing ***
Now the disclaimer is out of the way.
In stores , most freezers are fitted with over complicated alarms...They
have to meet food regulations.
1. Thermostat's
A temp sensor - hooked up outside to detection threshold device or circuit,
hooked up to a buzzer.
I remember when I was 10years old (some time ago) there are some temperature
switches
that you could connect to a battery and a buzzer... depending on your
electrical / electronic skill.
(backup battery and plug pack used as the power source)
Oh, yeah, I remember now - they are call thermostat's here's the 1st
search on google.
http://www.thermodisc.com/productdetail.asp?ProductID=2
If you are building only a few there will be other places that sell small
volumes.
Make sure the wires don't cause a poor seal on the door.
And there is no mucking around with the Hazardous mains (240/110V ac)
voltage.
2. Parallel Voltage measurement.
The mains failure might be a circuit beaker or mains power as you suggested.
This idea is cheeky but effective.... because is also not connecting
"directly" with
mains high voltage (240V/ 110V) (which is hazardous to your health)
- Put the fridge and a low voltage AC adapter in to the same power board or
2way power board.
something like this one (but for your country) http://tinyurl.com/2jjbbe
- Use the output of the AC adapter and connect to the coil terminals of
relay
(same voltage as the AC adapter's --> DC output)
- Wire the relay's Normally Closed(NC) terminal to the + side of a battery
- Wire the relay Common (C) terminal to a + side of DC buzzer same voltage
as the battery
- Wire the -side of the battery to the -side of the DC buzzer.
When the mains power is on the AC adapters DC output keeps the relay
contacts open between
(C) and (NC), the battery is off, not drawing any current.
When the mains power is off, the relay is de-energised and the (C) and (NC)
contacts connect causing the buzzer to go on.
It's cheeky because the when the power is off the buzzer will be on.. so
it's a sort of built in backup.
2. AC Mains Current detection
*** Dangerous unless you know what you are doing ***
I can see where you are going buy trying to measure the current, so nothing
is connected directly to the fridge....
but it will need battery backup if your whole house/building power fails.
Suffice to say you can use a type of current transformer.... sorry no more
details without knowing your electrical safety experience.
Joe
.
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